Abstract: A method for providing a test sample of concrete from a large poured area of concrete includes using a mold suitable for placement within the concrete form, the mold including a continuous sidewall and a bottom wall connected to the sidewall. An insert within the mold is spaced from the bottom wall so that a pressurization chamber is formed between the insert and the bottom wall of the mold. A fluid inlet is formed in the mold in fluid communication with the pressurization chamber and a fluid inlet tube is connected at a first end thereof to the fluid inlet. Preferably, the fluid tube is of a length sufficient to reach the surface of the concrete poured within the form. In one embodiment, a plurality of legs are formed on the insert to maintain the spacing of the insert from the bottom wall of the mold, the legs being separated sufficiently to allow fluid flow between them. In another embodiment, the space between the insert and the bottom of the mold is filled with a noncompressible fluid.

Abstract: An expansion-molded article is produced by filling prefoamed thermoplastic particles in a mold cavity formed in combination of mold sections, through each of which plural heating medium holes are defined, and then feeding a heating medium such as steam through the holes to heat and fusion-bond the particles into the article conforming with the mold cavity. Each of the mold sections is covered by a permeable porous sheet at least over the heating medium on a side of the mold cavity.

Abstract: An injection molding machine having a clamping unit and beams, which are disposed above the clamping unit and extend parallel and symmetrically to the vertical longitudinal plane of symmetry of the machine as far as to the rear end of the drive for the clamping unit. A pallet is provided, which is disposed over the drive and extends between the beams and has a supporting surface on which the moldings can be retained at predetermined locations, in which the moldings can be placed on the supporting surface by means of two carriages, which are horizontally movable in directions which are at right angles to each other. The carriages can be driven by flexible elements. Owing to such an arrangement, even delicate moldings can be removed from the injection molding machine, deposited and carried off quickly and in a gentle manner.

Abstract: The invention describes a method of conveying a sleeve (1) which is closed at one end and which consists of paper from a machining station (3) into a transporter. In order to be able to convey such sleeves into the transporter in a short time, even when the sleeves (1) are closed at one end by the integral moulding of a lid (2), it is according to the invention provided that the sleeve (1) be gripped at its edges (5) which are at the rear in the direction of movement (7) so that the sleeve is pushed in the direction of its longitudinal axis and on a straight path into the transporter, air being blown into the interior (16) of the sleeve (1). To this end, a scraper (4) is used which is adapted for translatory movement.

Abstract: A method for producing a sleeve having a closed end by extruding a forming material from a mouthpiece. A core member is arranged in position in the mouthpiece and has a piston member detachably provided in a tip end of the core member. The piston member has an air communication aperture. On the other hand, an outer die is arranged in the mouthpiece for forming an outer configuration of the closed end. As a result, an annular space is formed by the mouthpiece, core member and outer die. The forming material is then supplied into the annular space and extruded to form the closed end of the sleeve. After the outer die has been removed from the mouthpiece, the piston member is caused to slide relative to the mouthpiece and at the same time the air is blown into an inside of the closed end through the air communication aperture of the piston, while the forming material is further supplied and extruded from the mouthpiece to form the closed end sleeve.

Abstract: An apparatus for injection molding a substrate of an information recording disk in which melted molding material is injected into a mold space after a pair of mold bodies are clamped together. An uneven surface area is provided between a cutting device for cutting the cured molding material at the molding surface and an aperture for supplying the pressurized gas for causing the cured molding material to be released. The flow of pressurized gas through the cut portion of the cured molding material is prevented and force is generated by the pressurized gas causing the cured molding material and a stamper forming the molding surface to release uniformly from the mold.

Abstract: A gas accumulation space, in which a predetermined amount of a gas is to accumulate and which communicates with said gas passageway, is located in a mold. After a cavity of the mold has been filled with a synthetic resin but before the mold is opened, the gas is fed into the gas passageway and the gas accumulation space until the pressure of the gas in the gas passageway and the gas accumulation space reaches a predetermined value. After the pressure of the gas in the gas passageway and the gas accumulation space has reached the predetermined value, the gas passageway is closed at a position upstream from where the gas passageway communicates with the gas accumulation space.

Abstract: An injection molding device and a method for manufacturing a foil decorated molding use a first half of a mold and a second half of a mold with a transfer foil having a transfer layer on a substrate film transported into a space between the first half of the mold and the second half of the mold. A heating and removing device has a heating device and a molding removal device moved into the space to hold, with the removal device, a molding attached temporarily to the first half of the mold, and to heat the foil at the side of the second half of the mold with the heating device. When the first and second halves of the mold are closed, the heating and removing device is moved outside the space to remove the molding from the removal device.

Abstract: A process for producing an optical element wherein an optical molding is formed by using a mold and thereafter released from the mold by supplying a gas to the boundary between the mold surface and the optical molding. In the process, no localized external force is applied to the optical molding during the release thereof, and therefore undesirable deformation or flaws of the optical molding are not caused.

Abstract: An injection molding process creates a micro-cleanroom environment inside a mold cavity which can stay closed to airborne contaminants while ejecting and transferring the molded part out. The molded part is formed and solidified at a parting-line plane within the mold cavity, then is carried rearward on the movable mold insert to a second plane where it is stripped off and transferred out through a discharge aperture which is open when the mold cavity is in the second plane but closed off when in the first plane. The aperture faces substantially downward to prevent entry by upwelling thermal air currents. External supplied filtered gas can provide positive pressure through vents within the moldset's internal space. This maximizes mold and part cleanliness while speeding up "mold-open" cycle; may eliminate HEPA filters/enclosures and robots. Optical disks, lenses, food packaging and medical parts are suggested uses.

Abstract: A pneumatically operated mold ejection apparatus using a pneumatic pressure source exterior to a multiplate injection molding tool. The pressure source operates at least one knock-out pin disposed within a molding plate. Said pin is connected to a pneumatic piston spring loaded against a stop positioning the pin flush with the inner wall of the cavity during injection of plastic. The stop also positions the piston so that compressed air can reach the piston's surface when the pressure source is actuated. The piston includes a circumferential annular groove containing an O-ring for pneumatic sealing. The back side of the molding plate includes pneumatic channels between the cylinder and their intersection with a complimentary channel in the backing plate. These channels connect the system to the pressure source, and are surrounded by an O-ring trapped between the molding and backing plates for pneumatic sealing.

Abstract: A method and an apparatus for injecting a steam into a mold in an injection molding machine by injecting a desired stream toward the opening of the metal mold including a gate and cavities in connection with the opening and closing operation of the metal mold thereby intending the cooling solidification of the molten resin on th gate portion and simultaneously intending removal of dewing and an oily matter on the surface of the metal mold.

Abstract: An improved injection molding process for producing a substrate of an optical disc having a high quality is disclosed. The process includes the steps of: fixing a stamper having protrusions corresponding to pits for recorded information or a groove for tracking onto one mold unit of a pair of mold units of an injection molding machine; combining the mold units to form a closed cavity between the pair of mold units; charging a molten molding resin into the cavity; cooling the resin in the cavity to form a molded substrate; separating one mold unit from another mold unit; and releasing the molded substrate simultaneously from both mold units when the two mold units are separated from each other by applying pressurized air onto both sides of the substrate.

Abstract: Detaching a cured tire from mold sections of a tire mold during opening of the mold by communicating air under pressure into the space between the mold sections and confining the air in this space with a sleeve member supported on the upper mold section and slidably urged into sealing engagement with the lower mold section. Air under pressure is then communicated from the space between the mold sections to the spaces between the cured tire surface and the molding surfaces of the upper and lower mold sections to detach the tire. Sealing rings on the sleeve and on the upper mold section prevent leakage of the air under pressure from the space between the mold section. Spring means between the upper mold section and the sleeve member provide extension of the sleeve member into sealing engagement with the lower mold section.

Abstract: An improved machine for producing a configurated and specified weight product in die cavities of a rotary die roll, each of the die cavities being defined by a configurated sidewall and a porous bottom wall. During each revolution of the die roll, a batch of the product is forced into each cavity if the cavities pass a feed hopper. Upon continued rotation of the die roll, the bottom walls of the cavities are moved outwardly to force the configurated products from the die cavities, while simutaneously, air at a pressure greater than atmospheric pressure is directed through the porous bottom walls so that the configurated product is forced off of the bottom wall and onto a conveyor located beneath the die roll.

Abstract: A method and apparatus for manufacturing compression molded articles from a thermoplastic material blank comprising heating the material, and compression molding the blank by means of a die. The material forming the blank is deposited on the surface of an intermediate support which forms a part of the compression molding mold and extends under and is separated from the die. The blank is separated from the die, which may be accomplished using a heated stream of gas surrounding the die and directed at the point of separation. The blank is introduced into the mold which is closed as the intermediate support is lowered, followed by compression molding the blank by the application of compression molding pressure, and cooling the molded article at least partly under pressure.

Abstract: A process for the manufacture of injection molded articles out of material that is capable of being processed in an injection molding process comprising injection fluid material into a hollow space of a mold of a desired form, hardening or reacting the injected material at raised temperatures and subsequently separating the molded article from the mold at the same high tempeature by the aid of inert gas and/or air, pressed between the molded article and the mold, which is regulated by a self readjusting conical valve.

Abstract: An injection molding method for controlling the dimensions of a hollow plastic product by using a mold having a first and second mold parts; wherein one of the mold parts includes a retractable portion adjacent a gate. The retractable portion is movable between a protracted position and a retracted position while the mold is closed; and the mold parts define primary flow channels extending from the gate, which, when the retractable portion of the one mold part is protracted, direct initially injected molten plastic from the gate to create stabilizing regions of stiffened plastic. The method includes the steps of (a) protracting the retractable mold part; (b) injecting molten plastic from the gate and through the primary flow channels to create the stabilizing regions; (c) retracting the retractable mold part; (d) subsequently injecting additional molten plastic from the gate between the stabilizing regions into the side wall defining region of the mold cavity.

Abstract: A method for drain-casting a slip to obtain a substantially hollow molded article 42 is provided, by the use of an apparatus including a divisible mold 21 including an upper mold portion 22, a lower mold portion 23, and at least two side mold portions 24, 25 to form a mold cavity 38, each mold portion containing a filter member and a water-drainage means, and the lower portion having a slip supply duct 40.

Abstract: A sprue part is cut and removed from the injection mold part during the manufacture of information storage disks by an injection molding process. The highly sensitive molding of an information storage disk is protected from damage by the sprue and the deposition of dust particles during stripping by this process. The sprue is punched into a part serving as the die of the injection molding tool and subsequently removed, in particular by suction, through an orifice leading from inside the part, together with the dust particles generated in the punching process. Preferably, the sprue is punched out and removed with the injection molding tool closed. The injection molding tool must be opened only after the sprue and the dust have already been removed, thus ensuring that the molded product has an especially good quality.

Abstract: A device is disclosed which operates to receive and package automatically a plurality of articles molded cyclically and continuously by a high speed, high production injection molding machine where the articles are oriented, stacked or nested within a container in an orderly and antiseptic fashion.

Abstract: Tire mold vents (34) in communication with a sealed cavity (35) are pressurized for limiting the quantity of rubber entering the vents (34) and for assisting the stripping of the vulcanized tire (28) from the mold. Passages (40) in the mold communicate fluid pressure to the vents (34) and pressure regulators (58,60) control the fluid pressure communicated to the vents (34) during vulcanization and during ejection of the tire (28) from the mold (10).

Abstract: Apparatus and method are described for injection molding of thermoplastic paint cans substantially similar in size and design to the conventional steel one-gallon paint can. The apparatus comprises a cavity element defining the exterior of the container body and a core mold element including a peripheral lip protruding into the interior of the can body at a point below the upper terminus of the top circumference of the container body, thus providing a peripheral upwardly projecting edge. The cavity element includes a plurality of cam elements which move cooperatively on separation of the core and cavity elements. The cam elements grip the ridge of the container and expand it outwardly sufficiently to permit the core element of the mold to be removed from the container without hindrance from the inwardly protruding lip.

Abstract: A process is disclosed for forming at least one thin substantially uniform fluid coating comprising polymeric film forming material on a cylindrical mandrel, solidifying the fluid coating to form a uniform solid coating and separating the uniform solid coating from the mandrel. The process may comprise forming at least one thin substantially uniform fluid coating comprising polymeric film forming material around a cylindrical mandrel, the mandrel having a larger mass or lower thermal conductivity than the polymeric film forming material and a critical surface tension greater than the surface tension of the fluid coating, solidifying the fluid coating to form at least one thin substantially uniform solid coating comprising the polymeric film forming material around the cylindrical mandrel, heating both the uniform solid coating and the mandrel to a temperature at least above the apparent T.sub.

Abstract: There is disclosed a flexible mandrel for making tubular products comprising an elastomeric portion surrounding a reinforcing cable comprised of wire cables twisted around a non-metallic core. There is also disclosed a process for making a flexible mandrel and a process of making a hose using the flexible mandrel.

Abstract: A material handling device for transferring a formed good from an injection molding machine includes a pair of spaced tracks. Inner ends of the tracks are positioned below a mold carried by the machine with the track positioned transversely to opening and closing movement of the mold by the machine. On the track is a slidable basket which may be moved from the track inner end to an outer end away from the machine. Basket movement may be effected by activation of a pneumatic drive formed as part of the track and attached to the basket. During forming of a good, the basket is moved under the mold. When forming is complete, the mold opens and the good ejected. The good falls into the basket which has a cushion-like surface to inhibit damage. Opening of the mold starts a first timing period which lapses to activate the pneumatic drive to move the basket and good to the track outer end for good removal. During this first timing period the mold closes to begin a next forming cycle.

Abstract: The mold described herein comprises an upper and a lower portion in which the upper portion comprises an inverted cavity flash land mold section and the lower portion comprises a readily removable steel plate. By having the cavity flash land mold portion inverted and in the upper portion of the mold, the molded product is more easily separable by gravity from this upper mold portion which avoids the necessity to use means for lifting the molded product from the cavity and thereby avoids the distortions and stresses previously caused in the product by such lifting means. To aid in separating the product from the inverted cavity upper portion as the upper portion is separated from the lower flat sheet portion of the mold, releasing means, such as air from poppet valves in the upper area of the cavity mold, may be used to facilitate separation of the product from the upper cavity portion and deposition of this product on the lower flat sheet portion of the mold.

Abstract: The invention is concerned with the technical field of food article processing, and in particular relates to a method for shaping ice creams and articles of creamy consistency.The technical problem to be solved was that of quickly and accurately shaping articles of a creamy type with the same already provided with volume and consistency features which substantially approximate the final ones.The solution to the problem is provided by a method comprising at least one shaping step carried out by applying to said articles at least one air-pervious die and simultaneously blowing in air through said die.

Abstract: The present invention provides an injection mold apparatus for plastic piece molding. The apparatus includes male and female body parts and a gas blow-off ejection system for ejecting pieces formed on the male body part. The blow-off system includes side and top opening vents in the male body part for initial release and slight lifting of the piece and a further bottom positioned final blow-off vent, which is covered by slideable means during introduction of the plastic to the mold to prevent the plastic from flowing into the final blow-off vent and which is only exposed when required for completing blowing of the piece from the male body part. The slideable means has a slide tolerance to substantially eliminate flowing of the mold material therearound while being readily slideable when required for exposure of the blow-off vent to the male body part.

Abstract: A device for shaping ice cream into shaped articles, comprising extruder members (2) to deliver an ice-cream blank (3), cutter members (10) to subdivide the blank into a plurality of slugs (13) and conveyor for transporting the slugs (13) while being carried by trays (9) to a molding device (1). The molding device (1), which shapes the slugs of ice cream on the trays, comprises operative members (22, 23) to supply compressed air and at least one forming unit (15). The forming unit (15) includes an air pervious contoured die (16), formed by a porous material with a substantially uniform thickness, drive elements (19) for moving the die (16) toward the slugs of ice cream to be shaped, and walls defining an internal chamber (18) supplied by compressed air by the operative members (22, 23) and in communication with the die (16), to realize a uniform distribution of compressed air and a thin gap of air between the total surface of the shaped article and the surface of the die (16) facing the shaped article.

Abstract: A mold for use in heat expanding prefoamed polystyrene beads to form a part of a predetermined shape is disclosed. The mold comprises a cavity defined by separable mold wall portions. Each mold wall portion has on its exterior a chamber into which a heating medium is introduced to heat the mold walls and also into which cooling medium is introduced to cool the walls. A plurality of nozzles are provided in the mold walls and a corresponding plurality of tubes interconnect the nozzles to a manifold located in the corresponding chamber. A pressurized heating medium is introduced to the manifold whereby the heating medium is injected into the cavity to expand prefoamed polystyrene beads in the cavity. A device is provided on the manifold for the selective removal of condensate from the manifold. The mold construction provides for an economical, readily manufactured unit.

Abstract: A method of releasing an inner mold from a rubbery elastic molding having a corrugation in its inner longitudinal cavity and adapted suitably for, but not limited to, use in an electrical bushing or electrical insulator, which method comprises steps: forming a partial space connecting to a pressure source at an interface between the molding and the inner mold; supplying a pressure medium such as a gas or a liquid from the pressure source into the interface via said space to form a desired space between the molding and the inner mold over its entire zone and to expand the inner cavity of the molding; and releasing the inner mold from the molding.

Abstract: For heat-setting tubular articles (such as can bodies) of an at least partly biaxially oriented crystallizable polymer, preferably a saturated linear polyester such as polyethylene terephthalate, e.g. for thermally processable food containers, a tube of the polymer is fitted over a mandrel and clamped at its ends to the mandrel at a temperature below the glass transition temperature of the polymer. The tube is then heated, e.g. by inserting a heater 28 into the interior of the mandrel, above the temperature to which it is to be heat-set (at least 60.degree. C. above for PET) whereupon it shrinks into contact with the mandrel but is restrained from axial or further radial shrinkage. The tube and mandrel are cooled to below the heat-set temperature and the tube may then be cut into can body sections by knives engaging in circumferential grooves. Contact between the tube and mandrel is released, e.g.

Abstract: Method and apparatus are disclosed using a robot to load and unload precut pieces of sheet molding compound and the like between an upper die and a lower die of a sheet molding press.

Abstract: An article having a flange is molded between a mold core and a unitary mold cavity, the flange being formed during the process as a consequence of the existence of an undercut existing in a first surface of the cavity. A ridge is provided on a second surface of the mold cavity adjacent the undercut. A fluid, i.e., air, is injected between the cavity and the molded article as the core and cavity separate in such a volume and at such a pressure as will maintain the article in substantially complete and constant contact with the core as the core and article are withdrawn from the cavity. The flange conforms to the cavity wall until the article is free from the cavity, and subsequently the molded article is separated from the mold core.

Abstract: A disk which carries information obtained by molding from a cut matrix is detached from the matrix by means of a gas jet injected between the disk and the cut matrix. The disk is maintained in contact with the matrix both at the periphery and at the center, means being also provided for limiting deformation of the disk while it is being removed.

Abstract: Disclosed herein are a method and apparatus for opening molds by automatically unlocking a pair of locking mechanisms which cooperate to lock a pair of mold sections together. There are also disclosed herein a method and apparatus for handling a removed mold section and an article ejected from another mold section.

Abstract: A load-bearing part for aircraft or space vehicle is integrally made in a uniform manner from fiber-reinforced resin connecting endpieces of a small cross section merged via transition zones with a circular main- and central hollow. A particular method and particular tooling, for carrying out the method and making the hollow, are also disclosed.

Abstract: Cylindrical embossing tools are constructed from one or more masters formed by accurately scribing the face of a substrate along three axes in the face to produce a pattern of tetrahedrons. The plurality of masters, or replicated copies made from a single master, are assembled in a fixture and seamless copies are made by electrodeposition of nickel using various shielding and grinding methods to provide replicated copies of uniform thickness. The replicated copies are assembled and used to form larger electroforms until a generally cylindrical embossing tool of the correct width and circumference is created. Novel processes and apparatus are provided for removing the electroformed cylindrical tool from its mother cylinder.

Abstract: This relates to an apparatus for injection molding preforms for beverage bottles wherein a minimum cycle time is involved. Cores over which thermoplastic material is injection molded to form preforms for use in the blow molding of bottles are provided in sets and carried by a rotary turret so that as soon as the injection molded thermoplastic material has sufficiently set to permit its transfer with its associated core out of an injection mold cavity, the apparatus may be actuated to remove first injection molded preforms and thereafter immediately present a new set of cores to the injection mold cavities. This provides ample time for the cooling of the preforms so that when removed from the cores they will not be unduly deformed. In accordance with the feasible use of the apparatus, plural preforms, on the order of twenty-four and greater, may be formed with a cycle time on the order of 10-12 seconds.

Abstract: An apparatus for forming a thin-walled article comprising a frame providing a forming station for positioning a preheated sheet of thermoplastic material, first and second mold sections mounted on the frame in opposed relation with the forming station disposed therebetween, the first mold section having a forming cavity therein, the second mold section having a forming portion insertable in the forming cavity of the first mold section when the mold sections are displaced toward each other, the forming portion of the second mold section having at least one wall cooperable with at least one wall of the forming cavity of the first mold section when a preheated sheet of thermoplastic material is positioned at the forming station and the mold sections are displaced toward each other for sequentially shearing a blank from the preheated sheet of thermoplastic material and compressing the blank between the mold sections to cause the blank material to flow and form the article, means for ejecting the formed article fr

Abstract: There is provided an improvement in an injection molding apparatus for a container, where the apparatus includes a core defining the interior of the container and first means within the core for initiating ejection of a molded container from the core. The improvement consists of second means adjacent the rim of the molded container for blowing a gaseous material toward the container rim, thereby completing ejection by urging the container away from the core.

Abstract: A method of breaking loose a vulcanized hose from a rigid mandrel on which the hose has been vulcanized is described. A first end of the hose is clamped securely to prevent movement relative to the mandrel. The second end of the hose is clamped less securely so as to permit movement relative to the mandrel. Fluid pressure is thereafter introduced between the hose and the mandrel thereby causing the hose to increase in diameter and shorten in length, thus breaking the hose loose of its associated mandrel. The hose construction must be such that it will increase in diameter without rupture when subjected to sufficient internal pressure.

Abstract: A method of controlled ejection of a molded product in relation to orientation, speed of ejection and/or sterility is disclosed. The method is not dependent on auxiliary moving parts or vulnerable pins or blades. The molded product is ejected into a substantially enclosed guide conduit where the contours of the conduit substantially are regions of the parting surface and the cavity/ies. The guide conduit may be fairly holeproof, whereby a very fast ejection may be accomplished when the molded product is transported in an air stream in a manner similar to a pneumatic dispatch, not necessarily in a downward direction. The molded product may be kept sterile while it is transported in a stream of sterile air.

Abstract: A fluid-release mold is disclosed. The mold includes a preformed, porous mold body having a mold face formed on a first exterior surface and a second surface. A groove is formed in the second surface. A tape covers the groove to form a conduit between the surface of the groove and the surface of the tape facing the groove. The conduit directs pressurized release fluid to the mold. A fluid impermeable backing material is disposed over the second surface of the mold body whereby egress of the fluid from the conduit is prevented except through the mold body in a direction away from the second surface.

Abstract: An apparatus and method for separating a metal stamper from a metal mold on which the stamper is electro-formed. The gas flows between the mold and stamper to separate the stamper from the mold which are maintained separated by the vacuum applied to their back surfaces. Means is provided for centering the mold-stamper assembly between the backing plates just before the assembly is clamped between the backing plates. Means is provided for mechanically bending the outer peripheral portion of the mold-stamper assembly back and forth to separate the peripheral portion of the stamper from the mold.

Abstract: A method and apparatus for removing a flexible layer from a substantially flat mold or other surface. A curvilinear removal head, including a vacuum manifold holding one end of the flexible layer, pivots to peel the flexible layer from the mold.

Abstract: An apparatus for assisting in the removal of an ejection-molded article from the core of a mold is disclosed in combination with a molding machine in which the mold core is fixed to a moving platen and an ejector mechanism is supplied which mechanically removes the article from the core. The assisting apparatus includes a conduit leading to a surface of the mold core which defines the bottom of the article formed. A piston and cylinder is connected to the conduit, the interior of the cylinder being dimensioned to be approximately equal to the interior volume of the article formed. The cylinder is fixed with respect to the platen, while the piston is fixed with respect to the ejector apparatus.

Abstract: A hot sprue valve assembly is provided for controlling flow of molten material through a hot sprue bushing of an injection molding machine. The valve assembly is particularly designed for use with an injection molding machine for molding centrally apertured record discs, such as video information discs. The valve assembly includes a poppet valve movable between an open position to allow flow of molten disc-forming material into a mold cavity, and a closed position to prevent flow of the disc-forming material into the mold cavity. The poppet valve is designed to mold a central aperture in the disc upon movement to the closed position, and the valve assembly is designed to accommodate air ejector apparatus for removing a solidified record disc from the machine.

Abstract: Undercut tubular synthetic plastic articles, such as fittings, are formed in the mold cavity of an injection molding machine on a two-piece core a tubular component of which is surrounded by the undercut portion of the article and a first smaller-diameter portion at one side of the undercut portion. A cylindrical component of the core slidably guides the tubular component and is surrounded by a second smaller-diameter portion of the article at the other side of the undercut portion.